THE SANTAGATA FELTRIA LANDSLIDE (MARCHE REGION, CENTRAL ITALY) - CASEOF RECURRENT EARTHFLOW EVOLVING FROM A DEEP-SEATED GRAVITATIONAL SLOPE DEFORMATION

This paper examines the evolution of a large-scale earthflow located i n the northern sector of the Marche Region (central Italy). In this ar ea, mass movements of different typology are particularly frequent sin ce geological and geomorphological conditions often favour slope insta bility. Among these many mass movements, the one affecting the histori cal village of Sant'Agata Feltria has been chosen, also because its ev olution has been recorded in chronicles starting from ancient times. I n fact, reactivations of the 5.4 km long earthflow crossing the villag e have been quoted at least 12 times starting from the 16th century, e ven though more ancient activations have been inferred. Historic resea rches and geomorphologic analyses allowed the detailed reconstruction of the evolution and the mechanism of the phenomenon, outlining its ca uses and delineating risk zonation. In particular, a deep-seated gravi tational movement (lateral spreading) marked by trenches and ponds has been recognised at the top of the landslide. The earthflow has been i nterpreted as a more surficial side-effect of the deep-seated phenomen on, which constitutes its source area. It has also been highlighted th at reactivations coincided with long-lasting and intense rainfalls whi lst no direct connection seems to exist with earthquakes, even though the area is seismically rather active and seismic shocks could have be en among the major triggering factors for the deep-seated deformation. The oldest (and probably most catastrophic) recorded event itself (15 61 A.D.), took place during the first stages of a period of severe cli mate that involved the whole of Europe.